1. Field of the Invention
This invention relates to electrographic imaging apparatus and, more particularly, to an improved cleaning station for removing residual toner from an imaging surface.
2. Description of the Prior Art
Cleaning of residual particles from a reusable imaging surface of a photoreceptor in electrographic copiers is well known. In xerography, for example, a latent electrostatic image is optically formed on the imaging surface of the photoreceptor. This latent image is developed by depositing on it a charged finely divided, dry, electroscopic visible image developer material known in the art as toner. This developed toner image is then electrostatically transferred and permanently fixed to a support surface such as paper. However, after such transfer, residual toner remains on the photoreceptor. The residual toner is tightly retained on the photoreceptor surface and is difficult to remove. This retention is believed to be caused both by electrical charge attractions and other forces that prevent complete transfer of the toner to the imaging surface. Since residual toner can cause imperfections in subsequent copies, cleaning of residual toner from the photoreceptor must be accomplished rapidly and thoroughly.
Conventional photoreceptor cleaning stations typically include one or more rotatable cleaning brushes which frictionally scrub the imaging surface of the photoreceptor to remove residual toner from it. The removed toner is then exhausted by a vacuum system.
The vacuum system may not remove all the toner from the cleaning brush, and the brush may accumulate toner to such extent that it becomes overloaded with toner. An overload cleaning brush can deposit toner back onto the photoreceptor and cause a dark background on copy sheets. Further, an overloaded cleaning brush can scratch the photoreceptor. Still further, an overloaded brush can produce a cloud of toner dust which can leak out of the cleaning station and contaminate other machine components.
Various structures have been employed to aid vacuum systems in removing toner from cleaning brushes. One such structure is a stationary flicker bar that deformably engages the brush nap to mechanically remove toner from it. Flicker bars, however, tend to generate clouds of the toner dust which can cause machine contamination.
U.S. Pat. No. 3,644,959 discloses an arrangement, somewhat similar to a flicker bar structure, wherein toner is removed from a cleaning brush by means of a plurality of rotatable thin disks which agitate the nap of the cleaning brush. Such an arrangement can create a significant amount of toner dust which can escape out of the cleaning station and damage vital machine components.